content: /*
   * Copyright 2016 David Karnok
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package hu.akarnokd.agera;
  
  import android.support.annotation.NonNull;
  
  import com.google.android.agera.Condition;
  import com.google.android.agera.Observable;
  import com.google.android.agera.Updatable;
  
  /**
   * Filters update() signals if the condition evaluates to false.
   */
  final class AgeraFilter extends AgeraSource<FilterUpdatable> {
      final Condition condition;
  
      AgeraFilter(@NonNull Observable source, @NonNull Condition condition) {
          super(source);
          this.condition = condition;
      }
  
      @NonNull
      @Override
      protected FilterUpdatable createWrapper(@NonNull Updatable updatable) {
          return new FilterUpdatable(updatable, condition);
      }
  }
  
  final class FilterUpdatable implements Updatable {
      final Updatable actual;
  
      final Condition condition;
  
      FilterUpdatable(Updatable actual, Condition condition) {
          this.actual = actual;
          this.condition = condition;
      }
  
      @Override
      public void update() {
          if (condition.applies()) {
              actual.update();
          }
      }
  }
  